Titanium and titanium alloys are useful for a wide variety of structural and engineering applications. Titanium and its alloys are generally characterized by low density, high stiffness, high strength, and good corrosion resistance. The aerospace industry is currently the predominant consumer of titanium and its alloys. Further, recent interest in using titanium has begun to increase in other industries such as the chemical, petrochemical, and medical industries. However, when compared to current hard metal alternatives, titanium and its alloys suffer from lower surface hardness, wear resistance, corrosion resistance, lower oxidation resistance, galling, and seizure of surfaces when in mechanical contact.
A number of methods have been developed to improve the surface properties of titanium and its alloys. For example, titanium surfaces can be coated with titanium nitride and titanium carbide using a number of known technologies such as ion implantation, laser gas nitriding, electron-beam surface alloying, and physical and chemical deposition. Further, boron alloying of titanium surfaces has been accomplished by techniques such as laser irradiation and electron-beam irradiation. Several of these methods have produced titanium having significantly improved surface properties. However, such methods frequently involve substantial equipment expense and extended production times which make the finished product relatively expensive. Additionally, several of these methods have limitations as to achievable coating thicknesses. Further, laser and electron beam methods also result in melting of surface regions of titanium which leads to oxidation of the metal, coarsening of surface structure and poor properties. Frequently, these methods also result in monolithic coating structures on titanium surfaces which tend to crack and spall under applied stresses.
For this and other reasons, the need remains for methods and materials which can improve the surface properties of titanium and its alloys, which have decreased manufacturing costs and improved resistance to wear and oxidation.